PPP1R1B and Huntington disease: It is important to recognize that a multitude of requirements need to be met for this therapy to be successful and several explanations need to be considered to account for our results: 1) STROC05 cells are not efficacious in HD, 2) insufficient cells survived to promote recovery, 3) there was an insufficient neuronal/DARPP-32 differentiation of cells, and 4) it is also conceivable that the R6/2 model might be too aggressive to evaluate hNSC as a restorative treatment.